Quasi one-dimensional magnetic nanostructures, such as nanorods, nanowires, and nanotubes have attracted significant scientific and technological interest because they exhibit unique magnetic properties not displayed by their bulk or nanoparticle counterparts. Crystalline magnetic nanorods belong to this class of magnetic materials known for their spontaneous magnetization. There are multiple potential uses for such nanostructures, such as: their use for high density magnetic recording media; their use in sensors; their use in spintronic devices, and their use in drug delivery applications.
A variety of methods have been proposed for synthesizing various types of nanorods. These synthetic methods are typically anisotropic growth with the intrinsic anisotropic crystal structure in a solid material, anisotropic growth using tubular templates, and anisotropic growth kinetically controlled by super-saturation or by using an appropriate capping surfactant. Other approaches to fabricate one-dimensional nanostructures include thermal evaporation and template assisted growth, vapor phase transport process with the assistance of metal catalysts, hydrothermal methods, and electrospinning.
The synthesis of discrete one-dimensional magnetic (iron) nanorods was reported by Park, S. L. et al. using the process of oriented attachment of monodisperse spherical nanoparticles [Park, S. J. et al., “Synthesis and Magnetic Studies of Uniform Iron Nanorods and Nanospheres”, J. Am. Chem. Soc. 2000, 122, 8581]. Puntes, V. F. et al. reported on the synthesis of cobalt nanodisks by means of thermal decomposition of the cobalt carbonyl precursors [Puntes, V. F. et al., “Colloidal Nanocrystal Shape and Size Control: The Case of Cobalt”, Science 2001, 291, 2115]. Dumestre, F., et al. reported on the synthesis of cobalt nanorods [Dumestre, F. et al., “Shape Control of Thermodynamically Stable Cobalt Nanorods through Organometallic Chemistry,” Angew, Chem. Int. Ed. 2002, 41, 4286], and Cordente, N. et al. reported on the synthesis of nickel nanorods by means of high-temperature reduction of organometallic complexes [Cordente, N. et al., “Synthesis and Magnetic Properties of Nickel Nanorods”, Nano Lett., 2001, 1, 565.].
While the above mentioned processes have met with varying degrees of success, they all are faced with the same common problems associated with chemical and physical processes, such as high cost, aggregation and coarsening of particles at elevated temperatures, and shape control, all of which limits their applications. Thus, there is a need in the art not only for more efficient methods of producing magnetic nanostructures, but also for magnetic nanostructures having unique morphologies.